Superconductivity is a phenomenon which allows the transference of electrical current without the loss of any energy, and in some cases allows the generation of an immensely powerful magnetic filed. Recent discoveries in the field of high temperature superconductivity have indicated that a series of mixed metal oxides that display the mechanical and physical properties of ceramics make superconductivity possible at temperatures far higher than previously thought possible.
Until recently, the only way to produce the phenomenon of superconductivity was to bathe the appropriate metals, initially mercury, tin and lead, and later metallic alloys, in liquid-helium. This exotic liquid is produced by lowering the temperature of rare and costly helium gas to 4.2 Kelvin, or -452.degree. Fahrenheit at which point it liquifies. The process, however, is expensive and requires considerable energy. Furthermore, unless the liquid helium is tightly sealed in a heavily insulated container, it quickly warms and vaporizes. Thus, the practical use of superconductors has been limited to a few devices such as an experimental magnetically levitated train, a few giant particle accelerators, and medical magnetic resonance imaging machines which operate with immense magnetic fields.
Recently, physicists have found that a class of ceramic compounds based upon YBa.sub.2 Cu.sub.3 O.sub.7, wherein Y is yttrium, a rare earth, allows superconductivity to be achieved at a temperature of 98.degree. K (-283.degree. F.). The substitution of other rare earths, even magnetic ones, for yttrium, in these ceramic compounds results in very little change in the resulting superconducting properties. This discovery suddenly made superconductivity practical. The problematic liquid helium could now be replaced as a coolant by liquid nitrogen which makes the transition from a gas at an easily produced temperature of 77.degree. K (-320.degree. F.). Moreover, liquid nitrogen is much cheaper, longer lasting, and more stable than helium. Further, these ceramics may be able to generate even more intense magnetic fields than metallic superconductors.
The problem is, however, that these ceramic materials are brittle in nature and therefore are difficult to make into flexible and malleable wires that can be used in magnetic coils and electric transmission lines. Additionally, there is a problem in keeping wires cooled to the appropriate temperature needed for superconductivity, and in reinforcing and structurally strengthening the brittle material.